The present invention is directed to .alpha.-hydroxy-, .alpha.-alkyl-substituted acetylene compounds.
Epoxy matrix composites have been widely used in aerospace products. However, epoxy matrix systems have drawbacks, not the least of which is that such systems are sensitive to moisture. Extended exposure to high humidity reduces the mechanical properties of cured epoxy systems at elevated temperatures. Accordingly, there has been considerable interest in polymers that could replace epoxies and which are significantly less sensitive to moisture, but which retain the desirable characteristics of the epoxies.
A variety of acetylene-terminated resin systems have been prepared and studied in recent years. Acetylene-terminated resins cure through addition rather than condensation, thus avoiding the problem of voids caused primarily by outgassing which occurs during the condensation mechanism cure.
One procedure for adding terminal acetylene groups to an oligomer comprises reacting the oligomer with a substituted terminal acetylene compounds containing at least three carbon atoms with an hydroxy group on the carbon atom adjacent the acetylene group, which may be converted to the desired acetylene terminated oligomer by base catalyzed cleavage. The preparation of acetylene terminated sulfone oligomers by this method is described in U.S. Pat. No. 4,356,325 to Harrison et al. The reaction of the sulfone with the terminal acetylenic compound is carried out in the presence of a palladium salt complex catalyst system and a cuprous salt promoter. A major problem associated with this process is removal of the metallic salts after the displacement reaction. Removal of both Pd and Cu to less than 20 ppm must be accomplished; otherwise premature crosslinking of the acetylene groups can take place leading to poor mechanical performance. Although treatment with a dialkylor trialkyl-amine does remove these metals in monomeric small molecules, it is extremely difficult to remove the metals from higher molecular weight oligomers.
Another procedure for adding terminal acetylene groups to an oligomer comprises reacting the oligomer with the metallic salt of m-hydroxyphenylacetylene, as disclosed in U.S. Pat. No. 4,108,926 to Arnold et al. The metallic salt is, however, difficult to synthesize and expensive to produce. The synthesis comprises treatment of 3-hydroxyacetophenone with tosyl chloride to form the tosylated acetophenone, which is thereafter treated with phosphorus oxychloride and DMF to form .alpha.-chlorocinnamaldehyde-3-yl(p-toluenesulfonate). Hydrolysis of the latter compound with KOH yields the potassium salt of m-hydroxyphenylacetylene.
Accordingly, it is an object of the present invention to provide a new method for adding terminal acetylene groups to a molecule.
Another object of the present invention is to provide a novel acetylenic end-capping agent for oligomers.
A further object of the present invention is to provide a method for preparing novel acetylenic end-capping agents.
Other objects, aspects and advantages of the present invention will be apparent to those skilled in the art from a reading of the following disclosure.